Guide to Hidden Mold in Rental Homes, Apartments, Offices

HIDDEN MOLD RISKS for RENTERS - The mold you see or the mold you tested may not be the only concern nor the main risk. How to handle hidden or "non-visible" mold contaimnation complaints or problems in rental property, apartments, rental homes, offices, Hidden mold contamination testing advice for rental tenants or Hidden mold contamination complaint advice for landlords

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This article describes the steps that a tenant in a rental apartment or rental home can take to look for and test for
hidden mold contamination, we discuss when such testing is appropriate, and we make suggestions on how to inform building management of a mold problem, what to expect the rental property managers to do if they
are going to address a mold problem properly, and what the rental apartment tenant needs to watch out for during
a mold investigation and mold remediation of their home.

A Guide to Possible Hidden Mold in Rental Apartments, Houses, Offices

The mold that you *see* may not by any means be the whole problem, or even much of the problem; various species could be
in building cavities and in the HVAC system.

Too often we find that "black mold" on building surfaces has received attention but hard-to-see Penicillium sp. or Aspergillus sp. (for example) remain in large reservoirs on building surfaces or in insulation.

Magic bullets: Also, "bleaching mold" or "fogging" or "encapsulating" mold is never a successful remedy for a moldy building.

The places where mold is growing must be found, moldy material removed, exposed surfaces cleaned, and the causes of mold
growth corrected.

If the area of mold growth is large (more than 30 sq ft) the work needs to proceed with special
procedures to avoid spreading moldy dusty debris around.

Tenant-identified possible mold reservoirs

The tenant or building maintenance staff may have already identified apparent mold reservoirs or sources, and of course there could be other sources from other leaks or problems they haven't
discovered:

Roof leaks - can have leaked into ceilings and walls; depending on what building materials used, they could be moldy with
problem molds.

HVAC systems - If there is a common A/C duct system which has become mold contaminated, no amount of cleaning in your immediate
apartment would be sufficient since it is possible that the whole system needs to be cleaned, or possibly some duct
sections replaced, and the cause corrected. Also it is common for A/C condensate or water from a chiller system to
leak; water could have leaked into your closet ceiling and walls, also creating a problem mold reservoir.

Building insulation - often building insulation has become mold contaminated but looks "clean" to the naked eye. Few mold inspectors test this material, yet it is often discovered to be the principal problem mold reservoir in some building areas.

Very often when I visit a site I find other leaks and mold sources that need to be addressed, so I wouldn't assume these
are the full extent of what needs attention.

Frequently Asked Questions (FAQs)

Question:

Is it safe to have plastic flooring over a wood floor over a concrete slab foundation, regardless of anything else, or is the plastic flooring a moisture trap that would probably cause a mold buildup even without a flooded foundation for two months? Has anyone looked at this? At all?
I looked at the Building Code of Canada, hoping it would helpfully say "Don't ever do this!!!!!" and it doesn't, alas.

My landlord put the plastic layer down about 6-7 years ago. In the bathroom (currently gutted) there was wood over concrete, and ceramic and vinyl over the wood, and the wood had rotted in multiple locations. In the kitchen there is linoleum/vinyl over wood over concrete. The floor under the sink is rotted and the boards elsewhere are warped, but the city hasn't ordered the landlord to fix it. I have no idea what's going on under the plastic in the main area because I don't know how to have a look without causing damage. I'm looking for ammunition to get the floors in the main room/kitchen officially looked at.

I can't afford to pay a consultant (on disability in Montreal) but was hoping that you could point me to something that might help. I didn't see anything on Inspectapedia but maybe don't know what to look for. If you want more details I can send you them.
Thank you for all the information you do have on mold. It's been very helpful. - A.C., Montreal, 11/21/2013

Reply:

I agree that this topic has not been pinned down, as I will explain in a moment. A competent onsite inspection by an expert usually finds additional clues that would permit a more accurate, complete, and authoritative answer than we can give by email alone. You will find additional depth and detail in articles at our website.
That said I offer these comments:
I have observed that trapped moisture within a floor structure indeed will ultimately rot the materials. All mold is everywhere all the time - it's the concentration that varies.

So all we need is a few mold spores of wood rotting fungus to have been present when a floor, perhaps dry at the time, was enclosed and sealed such that later water entry from below initiates mold growth and rot.
But still, I have inspected a number of floor structures built on concrete that were sealed from above and later disassembled to show no rot damage.

The key variable, as you pose, is leaks and water entry. In short, if the building does not leak from above or up from below through the foundation or slab, the enclosed floor cavity, say sleepers on concrete, topped with perhaps subflooring, finish flooring, and tile or laminate or vinyl sheet flooring, survives quite well.

If the same floor structure cavity is wet from any source and is not opened and dried promptly mold growth and later rot can be expected to develop.

I believe that the codes are silent on this point because of the variables involved and the anticipation that good building design and proper maintenance is not supposed to tolerate water entry up through the floor of an occupied space. In other words, build and maintain your building to keep water out.

That approach is probably more cost-effective and easier to specify than to try to make every single indoor component able to withstand flooding.
To be clear, we could just as well say don't ever enclose a wall or ceiling, because water can get in and cause trouble.

But we do enclose them. (And water does leak in and cause trouble.)
Moving on to the specific case you describe,
re: "The floor under the sink is rotted and the boards elsewhere are warped, but the city hasn't ordered the landlord to fix it."
suggests to me that

- there are building leaks that need to be corrected, and that are causing costly damage to the building

- If typical building materials used such as drywall & fiberglass insulation are being wet, there is a reasonable risk of problematic mold contamination indoors too.

Please take a look at the article series I've written specifically for people in your situation, beginning at RENTERS & TENANTS: MOLD ADVICE and let me know if questions remain after you've seen that material.

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The Home Reference Book - the Encyclopedia of Homes, Carson Dunlop & Associates, Toronto, Ontario, 25th Ed., 2012, is a bound volume of more than 450 illustrated pages that assist home inspectors and home owners in the inspection and detection of problems on buildings. The text is intended as a reference guide to help building owners operate and maintain their home effectively. Field inspection worksheets are included at the back of the volume. Special Offer: For a 10% discount on any number of copies of the Home Reference Book purchased as a single order. Enter INSPECTAHRB in the order payment page "Promo/Redemption" space. InspectAPedia.com editor Daniel Friedman is a contributing author.

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Allergen Tests in Buildings advice about how to test, what to look for, in evaluating the level of dog, cat, or other animal allergens in a building

"IgG Food Allergy Testing by ELISA/EIA, What do they really tell us?" Sheryl B. Miller, MT (ASCP), PhD, Clinical Laboratory Director, Bastyr University Natural Health Clinic - ELISA testing accuracy: Here is an example of Miller's critique of ELISA
http://www.betterhealthusa.com/public/282.cfm - Townsend Letter for Doctors and Patients
The critique included in that article raises compelling questions about IgG testing assays, which prompts our interest in actually screening for the presence of high levels of particles that could carry allergens - dog dander or cat dander in the case at hand.
http://www.tldp.com/issue/174/IgG%20Food%20Allergy.html contains similar criticism in another venue but interestingly by the same author, Sheryl Miller. Sheryl Miller, MT (ASCP), PhD, is an Immunologist and Associate Professor of Basic and Medical Sciences at Bastyr University in Bothell, Washington. She is also the Laboratory Director of the Bastyr Natural Health Clinic Laboratory.

Allergens: Testing for the level of exposure to animal allergens is discussed at http://www.animalhealthchannel.com/animalallergy/diagnosis.shtml (lab animal exposure study is interesting because it involves a higher exposure level in some cases

Fifth Kingdom, Bryce Kendrick, ISBN13: 9781585100224, is available from the InspectAPedia online bookstore - we recommend the CD-ROM version of this book. This 3rd/edition is a compact but comprehensive encyclopedia of all things mycological. Every aspect of the fungi, from aflatoxin to zppspores, with an accessible blend of verve and wit. The 24 chapters are filled with up-to-date information of classification, yeast, lichens, spore dispersal, allergies, ecology, genetics, plant pathology, predatory fungi, biological control, mutualistic symbioses with animals and plants, fungi as food, food spoilage and mycotoxins.